DefaultValue.h

Classes

Global Functions -- A templated function which sets a variable to a default value. (full description)

A templated function which sets a variable to a default value. (source)

Interface

inline void defaultValue(T &theValue)

Description

Review Status

Reviewed By:

syang@nrao.edu

Date Reviewed:

1996/03/14

Programs:

Tests:

tDefaultValue.cc

Prerequisite

none

Etymology

The DefaultValue function name is derived from its use to fill a data type with a default value, usually zero.

Synopsis

The DefaultValue function is passed an instance of a data type and the variable is filled with a default value. The majority of classes may use the templated version here. Special classes may use their own non-templated specializations as demonstrated in ../Utilities/test/tDefaultValue.cc.

Example

    Int foo = 35;
    defaultValue(foo);
    AlwaysAssert(foo == 0, AipsError);
    Array<Float> bar;
    defaultValue(bar);
    AlwaysAssert(allEQ(bar, 0.0f), AipsError);

A special class may need its own implementation:

    void defaultValue(MySpecialClass &val){
     // make a default value be all zeros
     val.operator()(IPosition(2,3,4)) = Table.keywords().defaultval();
    };

Motivation

We needed a common way of setting all objects to zero or some null/default value. Specializing a templated function seemed the only way to reach everyone.